The interest in fuel cell systems is in its ascendancy, due in part to the ability of such systems to provide clean, reliable power for various applications that require the production of electricity or related useful power. In a typical fuel cell configuration, an electrolyte is sandwiched between electrodes (specifically, an anode and a cathode) such that positive ions generated at the anode flow through the electrolyte and react with ions generated at the cathode, while current generated by the flow of free electrons produced at the anode can be used to power one or more external devices. Some fuel cells require the presence of a catalyst material to promote the formation of positive and negative ions on the anode and cathode, respectively. In addition, by stacking individual fuel cells relative to one another, more powerful systems can be built.
In many fuel cell systems, hydrogen or a hydrogen-rich gas is supplied through a flowpath to the anode side of a fuel cell while oxygen (such as in the form of atmospheric oxygen) is supplied through a separate flowpath to the cathode side of the fuel cell. These flowpaths route the supply of gaseous fuel and oxygen to their respective porous electrodes to ensure that the gases come into contact with the catalyst material disposed on or adjacent the electrodes. After the gaseous fuel and oxygen are routed through their respective flowpaths and pass through the interstices of corresponding porous electrodes, they encounter a layer of catalyst. Upon contact with the catalyst on the anode, the hydrogen is ionized and migrates through the membrane situated between the anode and cathode of each fuel cell. The ionized hydrogen then combines with oxygen that has been ionized at the cathode. Together, the ionized hydrogen and oxygen form water as a non-polluting reaction product. Supplemental humidifying devices also introduce water into the fuel cell structure. The presence of this water can be a problem when the fuel cell system is switched off in an environment where the temperature falls below the freezing point of water, as the moisture present therein could solidify and block the fuel and oxygen flow routes, thereby making renewed start-up of the fuel cell system difficult or impossible. Accordingly, there exists a need for a PEM fuel cell system design and mode of operation that accounts for the presence of water, water-based mixtures or other freezable reaction products in the fuel cell system.